The Delimiter property returns a string which specifies the
path delimiter used for the current mailbox. If the IMAP server
supports multiple levels of mailboxes, then a special character or
sequence of characters are used as delimiters between different
levels of the mailbox hierarchy. On most systems, including most UNIX
and Windows platforms, the delimiter is the forward slash
"/" character.
It is possible that an IMAP server may only support a flat
namespace, in which case this property will return an empty
string.